Bridge plan best for history by far worst in other ways

Thursday

Jun 23, 2011 at 2:00 AMJun 27, 2011 at 2:10 AM

The June 14 article "New support for all-wood bridge" demands comment.

The June 14 article "New support for all-wood bridge" demands comment.

The letter from the Advisory Council on Historic Preservation to the Federal Highway Administration supports the so-called "Alternative 1B" design for the Mitchell River Bridge in Chatham as the "best preservation alternative" at a life cycle cost that is allegedly "nearly

the same" as the other alternatives.

Whether 1B is the best of the seven proposed designs from a preservation perspective is questionable, but from both engineering and environmental perspectives it is unquestionably one of the worst. Alternative 1B incorporates preservative-treated wood pilings in tidal waters, a design that may not even be permitted by Massachusetts environmental agencies. Alternatives 3, 4 and 5 utilize concrete-filled tubular steel pilings, with no permitting issues and an expected life cycle two to five times longer than 1B's wood pilings.

The 1B draw span lift system has proved unreliable and troublesome in the past. Alternatives 3, 4 and 5 all utilize a modern, weather-protected, gear-driven draw span lift system.

As for life cycle costs, in the worst-case scenario, Chatham taxpayers face a $5.3 million to $8.5 million greater cost for Alternative 1B over 3, 4 or 5. Alternative 1B is not the best choice.